Lubricant additive and lubricating oil composition

ABSTRACT

Provided are (i) a lubricant additive including a borazine compound represented by the following general formula (1), (ii) a lubricating oil composition including a lubricating base oil and the lubricant additive, and (iii) a lubricating oil composition further including a friction modifier represented by the following general formula (2).

TECHNICAL FIELD

The present invention relates to a lubricant additive and a lubricatingoil composition.

BACKGROUND ART

For various machines represented by internal combustion engines,transmissions and the like, lubrication is an essential element forimproving energy efficiency and protecting machine parts from wear. Alubricant such as lubricating oil and a grease reduces friction and wearby forming a lubricating film on a friction surface. For the purpose ofreducing friction and wear even under a condition in which the frictionsurface is subjected to a large load and the thickness of thelubricating film is easily reduced, various load-resistant additivessuch as: oiliness agents which are adsorbed on the friction surface toform an oil film (e.g. higher fatty acids such as oleic acid, and higheralcohol esters); organic molybdenum based friction modifiers which reactwith the friction surface to form a film (e.g. molybdenumdithiocarbamate (MoDTC), and molybdenum dithiophosphate (MoDTP)); andfriction-reducing agents (e.g. dithiophosphate (ZnDTP), phosphoric acidester, and disulfide) are incorporated in the lubricant.

Regarding friction-reducing agents, phosphorus compounds such as theabove-mentioned ZnDTP and phosphoric esters are known to show a goodperformance as friction-reducing agents. However, for lubrication ofinternal combustion engines, a new friction-reducing agent is requiredwhich does not contain phosphorus, preferably does not containphosphorus or sulfur, in view of inhibiting poisoning of an exhaust gastreatment catalyst.

Regarding organic molybdenum based friction modifiers, sulfur-containingoil-soluble organic molybdenum compounds such as the above-mentionedMoDTC and MoDTP are known to show a good friction reducing effect undera boundary lubricating condition, and are widely used in combinationwith oiliness agent based friction modifiers so as to further improvethe friction reducing performance of the lubricating oil. However, MoDTCcontains a metal (ash) component and sulfur, and MoDTP contains ash,sulfur, and phosphorus. Therefore, it is pointed out that these organicmolybdenum based friction modifiers can be an interfering element inrecycling the lubricating oil for example, or that these organicmolybdenum based friction modifiers can badly affect an exhaust gaspurifier in a case where they are used for lubrication of an internalcombustion engine for example. From such viewpoints, it is required toreduce the additive amount of the organic molybdenum based frictionmodifier, and at the same time, it is required to improve theperformance of the oiliness agent based friction modifier, especially toimprove the friction reducing performance under boundary lubricatingconditions.

CITATION LIST Patent Literatures

-   Patent Literature 1: Japanese Patent Application Laid-Open No.    2003-021278-   Patent Literature 2: Japanese Patent Application Laid-Open No.    2006-089575-   Patent Literature 3: Japanese Patent Application Laid-Open No.    2007-186698-   Patent Literature 4: Japanese Patent Application Laid-Open No.    2009-221307

SUMMARY OF INVENTION Technical Problem

As lubricant components not including phosphorus or sulfur, inorganicsolid lubricant components such as a graphite powder and a hexagonalboron nitride powder (h-BN) are known (Patent Literature 1), and agrease composition containing such an inorganic solid lubricantcomponent is also suggested (Patent Literatures 2 to 4). Each of theseinorganic solid lubricant components microscopically has a layeredstructure, and interaction between adjacent layers is weak. Therefore,it is considered that the adjacent layers easily change their relativepositions when being subjected to a shearing force at the frictionsurface, thereby showing a lubricating effect.

However, since these inorganic solid lubricant components do not havesolubility or dispersibility, these inorganic solid lubricant componentsprecipitate when incorporated in a base oil as additive agents, whichcauses a serious problem of unevenness. Therefore, it is extremelydifficult to incorporate the inorganic solid lubricant components inordinary liquid lubricants represented by lubricating oil for internalcombustion engines. Greases (semisolid lubricant) disclosed in PatentLiteratures 2 to 4 are considered not to suffer problems in practicaluse, since the inorganic solid lubricant component is held by athickener in the greases. However, in view of improving microscopicuniformity, ease of mixing, and the like, it is preferable for acomponent incorporated in a grease composition to have solubility in thebase oil.

A first object of the present invention is to provide a lubricantadditive which has solubility in a base oil, does not include phosphorusor sulfur, and has a friction-reducing performance, and to provide alubricating oil composition including the lubricant additive.

A second object of the present invention is to provide a lubricating oilcomposition which includes an oiliness agent based friction modifier andshows improved friction reducing performance under boundary lubricatingconditions, with suppressed increase of phosphorus and sulfur content.

Solution to Problem

The inventor of the present invention has found that a compound having aBN six-membered ring as its basic skeleton, which is a smallest unitforming one layer of hexagonal boron nitride (h-BN), i.e. a borazinecompound has both solubility and anti-friction performance, and improvesthe friction reducing performance of the lubricating oil compositioncontaining an oiliness agent based friction modifier (ashless frictionmodifier) having a nitrogen atom in a polar group.

A first aspect of the present invention is a lubricant additiveincluding a borazine compound represented by the following generalformula (1), which achieves the first object.

(In the formula (1), R¹, R³, and R⁵ are each independently hydrogen, aC1 to C30 hydrocarbyl group, or a C1 to C30 hydrocarbyl group comprisinga heteroatom other than sulfur and phosphorus; and R², R⁴, and R⁶ areeach independently hydrogen, a C1 to C30 hydrocarbyl group, or a C1 toC30 hydrocarbyl group including oxygen or boron or nitrogen.).

In the present application, “or” means a logical sum unless otherwisenoted. In the present invention, the “heteroatom” is interpreted in abroad sense, and means elements other than carbon and hydrogen. Itshould be noted that a noble gas is not included in the “heteroatom”.

Regarding R¹, R³, and R⁵, a “C1 to C30 hydrocarbyl group includingoxygen or boron or nitrogen” can be given as one preferable embodimentof the above-mentioned “C1 to C30 hydrocarbyl group including aheteroatom other than sulfur and phosphorus”.

Regarding R¹, R³, and R⁵, a “C1 to C30 hydrocarbyl group includingoxygen or boron” can be given as another preferable embodiment of theabove-mentioned “C1 to C30 hydrocarbyl group including a heteroatomother than sulfur and phosphorus”.

In one preferable embodiment of the lubricant additive according to thefirst aspect of the present invention, in the above formula (1), R¹, R³,and R⁵ are the same groups and R², R⁴, and R⁶ are the same groups. Suchan embodiment allows easy production of the borazine compound.

A second aspect of the present invention is a lubricating oilcomposition including (A) a lubricating base oil, and (B) the lubricantadditive according to the first aspect of the present invention, whichachieves the first object.

A third aspect of the present invention is a lubricating oil compositionincluding (A) the lubricating base oil, (B) the lubricant additiveaccording to the first aspect of the present invention, and (C) afriction modifier represented by the following formula (2), whichachieves the second object.

(In the formula (2), p is 0 or 1; q is 0 or 1; r is 0 or 1; R⁷ is ahydrocarbyl group having no less than 8 carbon atoms; and R⁸, R⁹, andR¹⁰ are each independently hydrogen or a C1 to C4 hydrocarbyl group.).

In one preferable embodiment of the lubricating oil compositionaccording to the third aspect of the present invention, in the formula(2), at least R⁹ and R¹⁰ are hydrogen and where p and q are 1, R⁸, R⁹,and R¹⁰ are hydrogen. Such an embodiment makes it possible to increaseadsorption ability to the friction surface, whereby it becomes easy toincrease the friction-reducing effect.

One preferable embodiment of the lubricating oil composition accordingto the second or third aspect of the present invention further includesone or more selected from the group consisting of an ashless dispersant,an antioxidant, a friction modifier, a friction-reducing agent, ametallic detergent, a viscosity index improver, a pour point depressant,a corrosion inhibitor, an anti-rust agent, an anti-emulsifier, a metaldeactivator, a defoamer, and a coloring agent.

The lubricating oil composition according to the second or third aspectof the present invention can be preferably used for lubrication ofinternal combustion engines.

Advantageous Effect of Invention

According to the first aspect of the present invention, it is possibleto provide a lubricant additive having solubility in a base oil, notincluding phosphorus or sulfur, and having a friction-reducingperformance.

According to the second aspect of the present invention, by containingthe lubricant additive according to the first aspect of the presentinvention, it is possible to provide a lubricating oil composition whichhas improved friction-reducing performance, with suppressed increase ofphosphorus and sulfur content.

According to the third aspect of the present invention, it is possibleto provide a lubricating oil composition which contains an oilinessagent based friction modifier and which has further improved frictionreducing performance under boundary lubricating conditions, withsuppressed increase of phosphorus and sulfur content.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail. Itshould be noted that, unless otherwise noted, “A to B” regardingnumerical values A and B means “A or more and B or less”. In cases wherethe unit of the numerical value A is omitted, the unit given to thenumerical value B is applied to the numerical value A.

<1. Lubricant Additive>

The lubricant additive according to the first aspect of the presentinvention will be described.

(Borazine Compound)

The lubricant additive of the present invention includes a borazinecompound represented by the following general formula (1).

In the formula (1), R¹, R³, and R⁵ that are substituents on nitrogenatoms are each independently hydrogen, a C1 to C30 hydrocarbyl group, ora C1 to C30 hydrocarbyl group including a heteroatom other than sulfurand phosphorus.

Here, examples of the C1 to C30 hydrocarbyl group include, specifically,alkyl group which may be cycloalkyl group or alkylcycloalkyl group,alkenyl group in which double bond(s) may be in any position), arylgroup, alkylaryl group, arylalkyl group, and the like.

Examples of the above cycloalkyl group include C5 to C7 cycloalkylgroups such as cyclopentyl group, cyclohexyl group, and cycloheptylgroup. In the above alkylcycloalkyl group, alkyl substitution may be inany position of the cycloalkyl group.

Examples of the above aryl group include phenyl group, naphthyl group,and the like. In the above alkylaryl group and arylalkyl group, alkylsubstitution may be in any position of the aryl group.

The above “C1 to C30 hydrocarbyl group including a heteroatom other thansulfur and phosphorus” means a C1 to C30 hydrocarbyl groupfunctionalized to include a heteroatom other than sulfur and phosphorus.Examples of the hydrocarbyl group include the hydrocarbyl groups asabove. As examples of the above “heteroatom other than sulfur andphosphorus”, nonmetal typical elements other than phosphorus, sulfur,and noble gases can be given. Among them, oxygen O, boron B, nitrogen N,silicon Si, and halogen (fluorine F, chlorine Cl, bromine Br, and iodineI) can be given as preferable examples, and a group containing one ormore of these elements can preferably be employed. It should be notedthat, as the halogen, F and Cl are preferable, and F is more preferable,in view of bond stability.

Specific examples of functionalization include functionalization by anester bond (alkoxycarbonyl substitution or acyloxy substitution),functionalization by an acyl group, functionalization by a carboxy groupor metal salt thereof, functionalization by an ether bond (alkoxysubstitution), functionalization by a boryl group (e.g.dihydrocarbylboryl group), functionalization by a borate ester bond(e.g. dialkoxyboroxy substitution), functionalization by an amino group(e.g. dihydrocarbylamino group), functionalization by an amide bond(—CO—N<bond) (aminocarbonyl substitution or acylamino substitution),functionalization by a silyl group (e.g. trihydrocarbylsilyl group),functionalization by a halogeno group (e.g. fluoro group), and the like.

As a preferable embodiment of the above “C1 to C30 hydrocarbyl groupincluding a heteroatom other than sulfur and phosphorus”, a “C1 to C30hydrocarbyl group including oxygen or boron or nitrogen” can be given.The “C1 to C30 hydrocarbyl group including oxygen or boron or nitrogen”means a C1 to C30 hydrocarbyl group functionalized to include oxygen orboron or nitrogen. The above-described hydrocarbyl groups can be givenas the hydrocarbyl group.

Specific examples of the functionalization in this embodiment includefunctionalization by an ester bond (alkoxycarbonyl substitution oracyloxy substitution), functionalization by an acyl group,functionalization by a carboxy group, functionalization by an ether bond(alkoxy substitution), functionalization by a boryl group (e.g.dihydrocarbylboryl group), functionalization by a borate ester bond(e.g. dialkoxyboroxy substitution), functionalization by an amino group(e.g. dihydrocarbylamino group), functionalization by an amide bond(—CO—N<bond) (aminocarbonyl substitution or acylamino substitution), andthe like.

As another preferable embodiment of the above “C1 to C30 hydrocarbylgroup including a heteroatom other than sulfur and phosphorus”, a “C1 toC30 hydrocarbyl group including oxygen or boron” can be given. The “C1to C30 hydrocarbyl group including oxygen or boron” means a C1 to C30hydrocarbyl group functionalized to include oxygen or boron. Theabove-described hydrocarbyl groups can be given as the hydrocarbylgroup.

Specific examples of the functionalization in this embodiment includefunctionalization by an ester bond (alkoxycarbonyl substitution oracyloxy substitution), functionalization by an acyl group,functionalization by a carboxy group, functionalization by an ether bond(alkoxy substitution), functionalization by a boryl group (e.g.dihydrocarbylboryl group), functionalization by a borate ester bond(e.g. dialkoxyboroxy substitution), and the like.

Regarding each of R¹, R³, and R⁵ which is a substituent on nitrogen atomin the above general formula (1), in a case where it is a group otherthan hydrogen, its carbon number is preferably 3 or more, morepreferably 6 or more, and preferably 24 or less, more preferably 18 orless, and still preferably 12 or less.

In the above general formula (1), R², R⁴, and R⁶ that are substituentson boron atoms are each independently hydrogen, a C1 to C30 hydrocarbylgroup, or a C1 to C30 hydrocarbyl group including oxygen or boron ornitrogen.

Regarding R², R⁴, and R⁶, the C1 to C30 hydrocarbyl group is same as theC1 to C30 hydrocarbyl group described above regarding R¹, R³, and R⁵.

The above “C1 to C30 hydrocarbyl group including oxygen or boron ornitrogen” means a C1 to C30 hydrocarbyl group functionalized to includeoxygen or boron or nitrogen. The hydrocarbyl group described above canbe given as the hydrocarbyl group. Examples of embodiments of thefunctionalization include functionalization by an ester bond(alkoxycarbonyl substitution or acyloxy substitution), functionalizationby a carboxy group, functionalization by an ether bond (alkoxysubstitution), functionalization by a boryl group (e.g. dihydrocarborylgroup), functionalization by a borate ester bond (e.g. dialkoxyboroxysubstitution), functionalization by an amino group (e.g.dihydrocarbylamino group), functionalization by an amide bond(—CO—N<bond) (aminocarbonyl substitution or acylamino substitution), andthe like.

Regarding each of R², R⁴, and R⁶ which is a substituent on boron atom inthe above general formula (1), if it is a group other than hydrogen, thecarbon number thereof is preferably 3 or more, more preferably 6 ormore, and preferably 24 or less, more preferably 18 or less, and stillpreferably 12 or less.

In view of reducing volatility of the borazine compound, preferably oneor more of the six substituents R¹ to R⁶ in the above general formula(1) are groups other than hydrogen, more preferably two or more aregroups other than hydrogen, and especially preferably three or more aregroups other than hydrogen.

In addition, in view of easy production of the borazine compound, R¹,R³, and R⁵ that are substituents on nitrogen atoms are preferably thesame groups in the above general formula (1). From the same viewpoint,R², R⁴, and R⁶ that are substituents on boron atoms are preferably thesame groups in the above formula (1).

As the borazine compound satisfying these requirements, a borazinecompound in which all of the substituents (R¹, R³, and R⁵) on nitrogen,or all of the substituents (R², R⁴, and R⁶) on boron, or both of them(all of R¹ to R⁶) are groups other than hydrogen in the above generalformula (1) is especially preferably employed.

In the lubricant additive of the present invention, one borazinecompound represented by the above formula (1) may be used alone, or twoor more borazine compound represented by the above formula (1) may beused in combination.

(Production of Borazine Compound)

The method of producing the borazine compound represented by the aboveformula (1) is not particularly limited, and a known synthetic methodcan be adequately employed. For the sake of ease of explanation, a casewhere R¹, R³, and R⁵ that are substituents on nitrogen atoms are thesame groups, and R², R⁴, and R⁶ that are substituents on boron atoms arethe same groups is mainly described as an example. In this case, thesubstitution pattern of the borazine compound represented by the abovegeneral formula (1) can be classified in the following patterns (I) to(VI).

(I) N-hydrogen or aliphatic substitution, B-hydrogen;(II) N-hydrogen or aliphatic substitution, B-aliphatic substitution;(III) N-hydrogen or aliphatic substitution, B-aromatic substitution;(IV) N-aromatic substitution, B-hydrogen;(V) N-aromatic substitution, B-aromatic substitution;(VI) N-aromatic substitution, B-aliphatic substitution Hereinafter,examples of the synthetic method will be described for each of thepatterns (I) to (VI).

(Production of Borazine Compound: (I) N-Hydrogen or AliphaticSubstitution, B-Hydrogen)

In a case where R¹=R³=R⁵=hydrogen or an aliphatic group, andR²=R⁴=R⁶=hydrogen in the general formula (1), for example as shown bythe following formula (3), the borazine compound can be synthesized by amethod of reacting an alkali borohydride ABH₄ (A is an alkali metal)such as sodium borohydride and an ammonium halide RNH₃X (X is a halogen;R may have a cyclic structure (e.g. a cycloalkyl group), may have adouble bond, may be substituted by an aromatic group (e.g. an arylalkylgroup), and may be hydrogen) such as alkylammonium chloride in asolvent. Details such as the reaction conditions in the method aredisclosed for example in JP 2008-201729 A.

For another example, as shown in the following formula (4), the borazinecompound also can be synthesized by a method of reacting a borane (BH₃)complex such as borane-tetrahydrofuran complex or diborane (B₂H₆) and anitrile RCN (R is an aliphatic group (which may have a cyclic structure,and may have a double bond) or an aromatic group) in a solvent. Detailssuch as the reaction conditions in the method are disclosed for examplein JP 2010-173945 A.

For another example, the borazine compound can be synthesized by amethod of: synthesizing a trichloroborazine compound by reactingtrichloroborane BCl₃ and an ammonium halide RNH₃X (X is a halogen; R mayhave a cyclic structure (e.g. a cycloalkyl group), may have a doublebond, may be substituted by an aromatic group (e.g. an arylalkyl group),and may be hydrogen) such as alkylammonium chloride in a solvent asshown in the following formula (5); and thereafter reducing thetrichloroborazine compound by sodium borohydride as shown in thefollowing formula (6). Details of the reaction of the first step(formula (5)) such as the reaction conditions are disclosed for examplein JP 2005-112723 A and JP 2005-104869 A. The reaction of the secondstep (formula (6)) is well known.

(Production of Borazine Compound: (II) N-Hydrogen or AliphaticSubstitution, B-Aliphatic Substitution)

In a case where R¹=R³=R⁵=hydrogen or an aliphatic group, and R²=R⁴=R⁶=analiphatic group in the above general formula (1), for example, theborazine compound may be synthesized by a method of: synthesizing atrichloroborazine compound by reacting trichloroborane BCl₃ and anammonium halide RNH₃X such as alkylammonium chloride in a solvent asalready described referring to the formula (5); and thereafter reactingthe trichloroborazine compound and an aliphatic Grignard reagent R′MgX(X is a halogen; R′ may have a cyclic structure (e.g. a cycloalkylgroup), may have a double bond, and may be substituted by an aromaticgroup (e.g. an arylalkyl group)) as shown in the following formula (7).Details such as the reaction conditions in the method are disclosed forexample in JP 2005-053854 A, JP 2005-104869 A, and JP 2005-112723 A.

For another example, the borazine compound can be synthesized by amethod of successively reacting the above-described borazine compound of(I) N-hydrogen or aliphatic substitution and B-hydrogen, and an alkenecompound in two steps, under presence of a catalyst (e.g. RhCl(PPh₃)₃)(following formula (8)). Details such as the catalyst and the reactionconditions in the method are disclosed for example in JP 2010-037789 A.

(Production of Borazine Compound: (III) N-Hydrogen or AliphaticSubstitution, B-Aromatic Substitution)

In a case where R¹=R³=R⁵=hydrogen or an aliphatic group, and R²=R⁴=R⁶=anaromatic group in the above general formula (1), the borazine compoundcan be synthesized for example by a method of reacting theabove-described borazine compound of (I) N-hydrogen or aliphaticsubstitution, B-hydrogen and an aryl Grignard reagent (following formula(9)). Details such as the reaction conditions in the method aredisclosed for example in J. Am. Chem. Soc., 1959, 81, 582-586.

For another example, the borazine compound can be synthesized by amethod of reacting the above-described borazine compound of (I)N-hydrogen or aliphatic substitution, B-hydrogen and an aryl halide ArX(X is a halogen; Ar is an aryl group which may be substituted by analkyl group and the like), under presence of a catalyst (e.g.PdCl₂(PPh₃)₂) (following formula (10)). Details such as the catalyst andreaction conditions in the method are disclosed for example in JP2010-280637 A.

(Production of Borazine Compound: (IV) N-Aromatic Substitution,B-Hydrogen)

In a case where R¹=R³=R⁵=an aromatic group, and R²=R⁴=R⁶=hydrogen in theabove general formula (1), the borazine compound can be synthesized forexample by a method of: synthesizing a trihaloborazine compound byreacting a trihaloborane such as trichloroborane BCl₃ and an arylamineArNH₂ (Ar is an aryl group which may be substituted by an alkyl groupand the like) as shown in the following formula (11); and thereafterreducing the trihaloborazine compound by sodium borohydride as shown inthe following formula (12). Details of the reaction of the first step(formula (11)) such as the reaction conditions are disclosed for examplein JP 2005-170857 A. The reaction of the second step (formula (12)) iswell known.

(Production of Borazine Compound: (V) N-Aromatic Substitution,B-Aromatic Substitution)

In a case where R¹=R³=R⁵=an aromatic group, and R²=R⁴=R⁶=an aromaticgroup in the above general formula (1), the borazine compound can besynthesized for example by a method of: synthesizing a trihaloborazinecompound by reacting a trihaloboran such as trichloroborane BCl₃ and anarylamine ArNH₂ as described above referring to the formula (11); andthereafter reacting the trihaloborazine compound and an organometalliccompound formed by lithiation or transformation into a Grignard reagentof an aryl halide Ar′Y (Y is halogen; Ar′ is an aryl group which may besubstituted by an alkyl group and the like), as shown in the followingformula (13). Details such as the reaction conditions in the method aredisclosed for example in JP 2005-170857 A.

(Production of Borazine Compound: (VI) N-Aromatic Substitution,B-Aliphatic Substitution)

In a case where R¹=R³=R⁵=an aromatic group, and R²=R⁴=R⁶=an aliphaticgroup in the above general formula (1), the borazine compound can besynthesized for example by a method of: synthesizing a trihaloborazinecompound by reacting a trihaloborane such as trichloroborane BCl₃ and anarylamine ArNH₂ as described above referring to the formula (11); andthereafter reacting an aliphatic Grignard reagent R′MgX and thetrihaloborazine compound (following formula (14)), as described abovereferring to the formula (7).

(Production of Borazine Compound: Other Cases)

In the above explanation regarding the production method of the borazinecompound, embodiments where substituents on nitrogen atoms R¹, R³, andR⁵ are the same groups, and substituents on boron atoms R², R⁴, and R⁶are the same groups in the above general formula (1) have been explainedas examples. However, the borazine compound which can be employed in thepresent invention is not limited to these embodiments. Borazinecompounds having a substitution pattern in which substituents onnitrogen atoms R¹, R³, and R⁵ are different from each other, or in whichsubstituents on boron atoms R², R⁴, and R⁶ are different from each othermay also be employed, and such borazine compounds can also besynthesized. It is possible to synthesize the borazine compound having asubstitution pattern in which substituents on nitrogen atoms R¹, R³, andR⁵ are different from each other, the borazine compound having asubstitution pattern in which substituents on boron atoms R², R⁴, and R⁶are different from each other, or the borazine compound having bothsubstitution patterns, for example by: employing two or more ammoniumsalts or amines in combination as nitrogen sources of the borazinestructure; employing two or more organometallic reagent for introducingsubstituents on boron atoms of the borazine structure in combination;adequately adjusting the stoichiometric relationship between theB-unsubstituted borazine and the Grignard reagent in the reaction of theformula (9); employing different alkene compounds in the first step andthe second step in the reaction of the formula (8), and the like.

It is also possible to proceed the synthesis with the functional groupof the substituent protected by an appropriate protecting group, anddeprotect them after introducing all substituents. Introduction anddeprotection of protective groups can be carried out by a known method.It is also possible to introduce all substituents and thereaftertransform functional groups of the substituents to other functionalgroups by known synthetic methods.

(Use Application)

The lubricant additive of the present invention has solubility in a baseoil. Therefore, it can be incorporated in both of a lubricating oil(fluid lubricant) and a grease (semisolid lubricant), to improvefriction-reducing effect of the lubricants. In a case where thelubricant additive is contained in a lubricating oil, the contentthereof can be for example in a range of 0.01 to 5.0 mass %, as acontent of the borazine compound represented by the above generalformula (1) on the basis of the total amount of the lubricating oilcomposition as 100 mass %. In a case where the lubricant additive iscontained in a grease, as the content thereof, for example a range of0.1 to 10.0 mass % can be given as the content of the borazine compoundrepresented by the above general formula (1) on the basis of the totalamount of the grease composition as 100 mass %.

In addition, by incorporating the lubricant additive of the presentinvention in a lubricating oil (e.g. lubricating oil for internalcombustion engines), it is possible to improve not only afriction-reducing property of the lubricating oil but alsohigh-temperature detergency. Conventional friction-reducing agents usedin lubricating oils do not have a high-temperature detergent property.Therefore, the lubricant additive of the present invention can bepreferably used for lubrication of machines whose metal parts areexposed to a high temperature (e.g. internal combustion engines).

The principle of the lubricant additive of the present invention toincrease the high-temperature detergency has not been fully clarified.However, the inventor of the present invention presumes as follows. Thatis, in a borazine ring, B atoms and N atoms are alternately arranged toform a 6-membered ring, and polarization of B—N bonds makes threepartial positive charges and three partial negative charges form anelectric multipole. This particular electric multipole structure shows agood affinity with a highly polar sludge. On the other hand, theborazine ring structure itself has no polarity as a whole. Therefore,the lubricant additive shows a good affinity with the base oil as well.As a result, the lubricant additive exhibits a deterging effect evenunder a high-temperature condition.

<2. Lubricating Oil Composition (Second Aspect of Present Invention)>

The lubricating oil composition according to the second aspect of thepresent invention will be described. The lubricating oil compositionaccording to the second aspect of the present invention includes (A) alubricating base oil, (B) the lubricant additive according to the firstaspect of the present invention (hereinafter may be referred to as“borazine-based additive”).

((A) Lubricating Base Oil)

The lubricating base oil in the lubricating oil composition of thepresent invention is not particularly limited, and a mineral base oil ora synthetic base oil used for a general lubricating oil can be employed.

Specific examples of the mineral base oil include: a product made bypurifying a lubricating oil fraction obtained by vacuum distillation ofa residue of atmospheric distillation of a crude oil, by one or moretreatments of solvent deasphalting, solvent extraction, hydrogenolysis,solvent dewaxing, hydrorefining, and the like; an wax-isomerized mineraloil; a lubricating oil base oil produced by a method of isomerizing aGTL WAX (Gas To Liquid wax) produced for example by Fisher-Tropshprocess, and the like.

Examples of the synthetic base oil include: a poly a-olefin such as1-octene oligomer and 1-decene oligomer, and hydrogenation productthereof; isobutene oligomer and hydrogenation product thereof; paraffin;alkylbenzene; alkylnaphtalene; diesters such as ditridecyl glutarate,di(2-ethylhexyl) adipate, diisodecyl adipate, ditridecyl adipate, anddi(2-ethylhexyl) sebacate; polyol esters such as trimethylolpropanecaprylate, trimethylolpropan pelargonate, pentaerythritol2-ethylhexanoate, and pentaerythritol pelargonate;polyoxyalkyleneglycol; dialkyldiphenyl ether; and polyphenyl ether. Inaddition, aromatic synthetic oils such as alkylnaphthalene,alkylbenzene, and aromatic ester, and mixture thereof can be given asexamples.

In the lubricating oil composition of the present invention, a mineralbase oil, a synthetic base oil, or any mixture of two or morelubricating oils selected therefrom and the like may be employed as thelubricating base oil. One or more mineral base oil, one or moresynthetic base oil, a mixture oil of one or more mineral base oil andone or more synthetic base oil, and the like can be given as examples.

Kinematic viscosity, NOACK evaporation loss, and viscosity index of thelubricating base oil in the lubricating oil composition of the presentinvention may be adequately determined depending on the purpose of useof the lubricating oil composition. For example, in a case where thelubricating oil composition is used for internal combustion engines, thekinematic viscosity of the lubricating base oil at 100° C. may be 3.0 to16.3 mm²/s for example. Alternatively, for example in a case where thelubricating oil composition is used for transmissions, the kinematicviscosity of the lubricating base oil at 100° C. may be 3.5 to 25.0mm²/s for example.

((B) Borazine-Based Additive)

Details of the borazine-based additive have been already describedabove. The content of the borazine-based additive in the lubricating oilcomposition of the present invention is not particularly limited. As thecontent of the borazine composition represented by the above generalformula (1), it is normally 0.01 mass % or more, preferably 0.05 mass %or more, and especially preferably 0.1 mass % or more, and normally 5.0mass % or less, preferably 3.0 mass % or less, and especially preferably1.0 mass % or less, on the basis of the total amount of the composition.

<3. Lubricating Oil Composition (Third Aspect of Present Invention)>

The lubricating oil composition according to the third aspect of thepresent invention will be described. The lubricating oil compositionaccording to the third aspect of the present invention includes (A) thelubricating base oil, (B) the borazine-based additive, and (C) afriction modifier represented by the following general formula (2). The(A) lubricating base oil and the (B) borazine-base additive, and thecontents thereof are same as in the lubricating oil compositionaccording to the second aspect of the present invention.

((C) Friction Modifier)

In the general formula (2), p is 0 or 1. When p=0, the general formula(2) represents an amine compound.

When p=0, q is 0 or 1. When p=1 and q=0, the general formula (2)represents an amide compound.

When p=1 and q=1, r is 0 or 1. When p=1, q=1, and r=0, the generalformula (2) represents a urea compound. When p=1, q=1, and r=1, thegeneral formula (2) represents a ureide compound.

In the general formula (2), R⁷ is a hydrocarbyl group having no lessthan 8 carbon atoms. The carbon number of R⁷ is preferably no less than10, more preferably no less than 12; and preferably no more than 30, andmore preferably no more than 24.

Specific examples of the hydrocarbyl group having no less than 8 carbonatoms include an alkyl group (which may be substituted by cycloalkylgroup), alkylcycloalkyl group, alkenyl group (double bond(s) may be inany position), aryl group, alkylaryl group, arylalkyl group, and thelike.

Examples of the cycloalkyl group include a cycloalkyl group having 5 to7 carbon atoms, such as a cyclopentyl group, cyclohexyl group, andcycloheptyl group. Alkyl substitution of the cycloalkyl group may be inany position.

Examples of the aryl group and alkylaryl group include: an alkylphenylgroup such as a xylyl group, ethylphenyl group, propylphenyl group,butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenylgroup, octylphenyl group, nonylphenyl group, decylphenyl group,undecylphenyl group, and dodecylphenyl group; and aryl group andalkylaryl group having no less than 8 carbon atoms such as a substitutedor unsubstituted naphthyl group (preferably the alkyl group is a linearalkyl group; alkyl substitution of the aryl group may be in anyposition, and preferably in para position).

Examples of the arylalkyl group include an arylalkyl group having noless than 8 carbon atoms such as a phenylethyl group, phenylpropylgroup, phenylbutyl group, phenylpentyl group, phenylhexyl group(preferably the alkyl group is a linear alkyl group; aryl substitutionof the alkyl group may be in any position, and preferably in a position(opposite chain end from a position).

The hydrocarbyl group of R⁷ is preferably an alkyl group or alkenylgroup. When R⁷ is an alkenyl group, the alkyl groups between whichdouble bonds are interposed are preferably linear alkyl groups.

When R⁷ is an alkyl group, R⁷ is preferably a linear alkyl group. Inview of easy use under a low-temperature condition, it is morepreferable that R⁷ is an alkyl group having a methyl group in aposition. R⁷ being such an alkyl group makes it possible to lower thesolidifying point compared with a case where R⁷ is a complete linearalkyl group.

In the general formula (2), R⁸, R⁹, and R¹⁰ are each independentlyhydrogen or a C1 to C4 hydrocarbyl group. Preferably, at least eitherone of R⁹ and R¹⁰ is hydrogen, and more preferably both R⁹ and R¹⁰ arehydrogen. When p=1 and q=1 (that is, when R⁸ exists), preferably R⁸ ishydrogen, and more preferably R⁸, R⁹, and R¹⁰ are each hydrogen. Morehydrogen atoms being the groups other than R⁷ increase adsorbability toa friction surface, whereby it becomes easy to increase frictionreducing effect.

When p=0 in the general formula (2), the general formula (2) representsan amine compound. Such an amine compound can be adequately synthesizedby a known method.

When p=1 and q=0 in the general formula (2), the general formula (2)represents an amide compound. Such an amide compound can be adequatelysynthesized by a known method such as a condensation reaction of acarboxylic acid and an amine.

When p=1, q=1, and r=0 in the general formula (2), the general formula(2) represents a urea compound. A known synthetic method can be employedwithout particular limitations as the synthetic method of such a ureacompound. For example, a synthetic method by a condensation reaction ofan isocyanate compound and ammonia or an amine compound, as shown in thefollowing formula (15) can be given.

A known isocyanate compound can be used without particular limitationsas the isocyanate compound in the above formula (15). Examples of theisocyanate compound which can be used in the reaction represented by theabove formula (15) include an isocyanate compound in which R⁷ is ahydrocarbyl group (preferably an alkyl group or alkenyl group) having noless than 8 carbon atoms.

In addition, in the reaction represented by the above formula (15), aknown primary or secondary amine compound or ammonia can be used as anucleophilic reagent without particular limitations. Examples of theprimary or secondary amine compound which can be used in the reactionrepresented by the above formula (15) include an amine compound having ahydrocarbyl group having 1 to 4 carbon atoms.

In addition, when p=1, q=1, and r=1 in the general formula (2), thegeneral formula (2) represents a ureide compound. A known syntheticmethod can be employed as the synthetic method of such a ureidecompound, without particular limitations. For example, a syntheticmethod by a reaction of an acid chloride and urea or a urea compoundrepresented by the following formula (16) can be given.

A known acid chloride can be used as the acid chloride in the reactionrepresented by the above formula (16), without particular limitations.Examples of the acid chloride which can be used in the reactionrepresented by the above formula (16) include a carboxylic acid chloridein which R⁷ is a hydrocarbyl group (preferably an alkyl group or alkenylgroup) having no less than 8 carbon atoms.

A known urea compound can be used as the urea compound in the reactionrepresented by the above formula (16), without particular limitations.Examples of the urea compound which can be used in the reactionrepresented by the above formula (16) include urea, N-methylurea,N-ethylurea, N-tert-butylurea, N,N′-dimethylurea and the like. Theseurea compounds can be obtained by a known synthetic method such as areaction of isocyanate and ammonia or an amine compound.

As the (C) component in the lubricating oil composition of the presentinvention, an amide compound (p=1 and q=0 in the general formula (2)) ora urea compound (p=1, q=1, and r=0 in the general formula (2)) can beespecially preferably used in view of better friction reducing effectunder boundary lubricating conditions.

It should be noted that, the inventor of the present invention presumesas follows regarding the reason why the lubricating oil composition ofthe present invention exhibits an improved friction reducing performanceunder boundary lubricating conditions. That is: an h-BN sheet-like filmincluding boron and nitrogen is formed on a friction surface by the (B)component which is the borazine compound; the film is protected by the(C) component which is an ashless friction modifier having a nitrogenatom in a polar group interacting with the boron atoms of the film; andthe ashless friction modifier ((C) component) itself contributes to thefrication reduction effect, whereby the friction reducing effect issynergistically shown.

(Content)

The content of the friction modifier represented by the above generalformula (2) in the lubricating oil composition of the present inventionis, on the basis of the total amount of the composition, normally 0.01mass % or more, preferably 0.05 mass % or more, and especiallypreferably 0.1 mass % or more; and normally 10.0 mass % or less, morepreferably 5.0 mass % or less, and especially preferably 3.0 mass % orless.

(Other Additives)

The lubricating oil composition according to the second or third aspectof the present invention preferably further includes, aside from theabove-described lubricating base oil and the borazine-based additive,one or more selected from the group consisting of an ashless dispersant,an antioxidant, a friction modifier other than the above (B) componentand (C) component, a friction-reducing agent, a metallic detergent, aviscosity index improver, a pour point depressant, a corrosioninhibitor, an anti-rust agent, an anti-emulsifier, a metal deactivator,a defoamer, and a coloring agent. These additives may be contained inthe borazine-based additive together with the borazine compoundrepresented by the general formula (1).

As the ashless dispersant, a known ashless dispersant can be used. In acase where an ashless dispersant is contained in the lubricating oilcomposition of the present invention, the content thereof is, on thebasis of the total amount of the lubricating oil composition as 100 mass%, normally 0.01 mass % or more, and preferably 0.1 mass % or more; andnormally 20 mass % or less, and preferably 10 mass % or less.

As the antioxidant, a known antioxidant can be used. In a case where anantioxidant is contained in the lubricating oil composition of thepresent invention, the content thereof is, on the basis of the totalamount of the lubricating oil composition, normally 5.0 mass % or less,preferably 3.0 mass % or less; and preferably 0.1 mass % or more, andmore preferably 0.5 mass % or more.

As the friction modifier other than the (B) component and (C) component,a known friction modifier can be used. For example, oiliness agents suchas fatty acid esters, and molybdenum-based friction modifiers such as:sulfur-containing molybdenum complexes such as molybdenumdithiocarbamate and molybdenum dithiophosphate; sulfur-free organicmolybdenum complexes such as molybdenum-amine complex andmolybdenum-succinimide complex; and molybdenum disulfide, can be given.In a case where these friction modifiers are included in the lubricatingoil composition of the present invention, the content thereof is, on thebasis of the total amount of the lubricating oil composition, normally0.05 mass % or more, and preferably 0.1 mass % or more; and normally 5mass % or less.

As the friction-reducing agent, a known friction-reducing agent can beused. For example, phosphorus compounds such as (mono, di, or tri-thio)phosphorous or phosphoric triesters and zinc dithiophosphate, andsulfur-containing compounds such as disulfides, olefin sulfides,sulfurized fatty oils, and dithiocarbamates can be given. In a casewhere these friction-reducing agents are contained in the lubricatingoil composition of the present invention, the content thereof is, on thebasis of the total amount of the lubricating oil composition, normally0.005 mass % or more and 5 mass % or less.

As the metallic detergent, a known metallic detergent can be used. Forexample, alkali metal sulfonates, alkaline earth metal sulfonates,alkali metal phenates, alkaline earth metal phenates, alkali metalsalicylates, alkaline earth metal salicylates, and mixture thereof canbe given. These metallic detergents may be overbased. In a case wherethese metallic detergents are contained in the lubricating oilcomposition of the present invention, the content thereof is notparticularly limited. In a case where the lubricating oil composition isfor internal combustion engines, the content thereof is, on the basis ofthe total amount of the lubricating oil composition, normally 0.01 mass% or more and 5 mass % or less in terms of metal element.

As the viscosity index improver, a known viscosity index improver can beused. For example, a so-called non-dispersive viscosity index improversuch as a polymer or copolymer of monomers of one or two or moreselected from various methacrylic acid esters and hydrogenated productsthereof, a so-called dispersive viscosity index improver obtainable bycopolymerizing various methacrylic acid esters including a nitrogencompound, a non-dispersive or dispersive ethylene-a-olefin copolymer anda hydrogenated product thereof, polyisobutylene and a hydrogenatedproduct thereof, a hydrogenated product of styrene-diene copolymer,styrene-maleic anhydride ester copolymer, polyalkylstyrene, and the likecan be given. The weight average molecular weight of the viscosity indeximprover is, for example in a case where a dispersive or non-dispersivepolymetacrylate is used, normally 5,000 or more and 1,000,000 or less.For example in a case where polyisobutylene or a hydrogenated productthereof is used for an internal combustion engine, the number averagemolecular weight is normally 800 or more and 5,000 or less. For examplein a case where the ethylene-a-olefin copolymer or a hydrogenatedproduct thereof is used for an internal combustion engine, the numberaverage molecular weight is 800 or more and 500,000 or less.

In a case where these viscosity index improvers are contained in thelubricating oil composition of the present invention, the contentthereof is, on the basis of the total amount of the lubricating oilcomposition, normally 0.1 mass % or more and 20 mass % or less.

As the pour point depressant, a known pore point depressant such as apolymethacrylate-based polymer can be adequately used depending on theproperty of the lubricating base oil to be used. In a case where thepour point depressant is contained in the lubricating oil composition ofthe present invention, the content thereof is, on the basis of the totalamount of the lubricating oil composition, normally 0.01 to 1 mass %.

As the corrosion inhibitor, a known corrosion inhibitor such as abenzotriazole-based compound, tolyltriazole-based compound,thiadiazole-based compound, and imidazole-based compound can be used. Ina case where these corrosion inhibitors are contained in the lubricatingoil composition of the present invention, the content thereof is, on thebasis of the total amount of the lubricating oil composition, normally0.005 mass % or more and 5 mass % or less.

As the anti-rust agent, a known anti-rust agent such as a petroleumsulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate,alknylsuccinic acid ester, and polyhydric alcohol ester can be used. Ina case where these anti-rust agents are contained in the lubricating oilcomposition of the present invention, the content thereof is, on thebasis of the total amount of the lubricating oil composition, normally0.005 mass % or more and 5 mass % or less.

As the anti-emulsifier, a known anti-emulsifier such as a polyalkyleneglycol nonionic surfactant such as polyoxyethylene alkyl ether,polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthylether can be used. In a case where these anti-emulsifiers are containedin the lubricating oil composition of the present invention, the contentthereof is, on the basis of the total amount of the lubricating oilcomposition, normally 0.005 mass % or more and 5 mass % or less.

As the metal deactivator, a known metal deactivator such as imidazoline,pyrimidine derivative, alkylthiadiazole, mercaptobenzothiazole,benzotriazole and derivatives thereof, 1,3,4-thiadiazole polysulfide,1,3,4-thiadiazolyl-2,5-bisdialkyl dithiocarbamate,2-(alkyldithio)benzoimidazole, and β-(o-carboxybenzylthio)propionitrilecan be used. In a case where these metal deactivators are contained inthe lubricating oil composition of the present invention, the contentthereof is, on the basis of the total amount of the lubricating oilcomposition, normally 0.005 mass % or more and 1 mass % or less.

As the defoamer, a known defoamer such as a silicone, fluorosilicone,and fluoroalkylether can be used. In a case where these defoamers arecontained in the lubricating oil composition of the present invention,the content thereof is, on the basis of the total amount of thelubricating oil composition, normally 0.0005 mass % or more and 1 mass %or less.

As the coloring agent, a known coloring agent such as an azo compoundcan be used.

The lubricating oil composition according to the second aspect of thepresent invention has an improved friction-reducing performance bycontaining the (B) component (the borazine-based additive); therefore itcan be preferably employed for lubrication of various machines. Inaddition, it has an improved high-temperature detergency as describedabove; therefore, it can be especially preferably used for lubricationof machines whose metal parts are exposed to a high temperature (e.g.internal combustion engines). Specifically, it can be especiallypreferably used for lubrication of internal combustion engines in whichphosphorus and sulfur content and the like that migrates into theexhaust gas need to be taken into consideration (e.g. internalcombustion engine equipped with an exhaust gas processing apparatus).

By containing the borazine-based additive as the (B) component inaddition to the (C) component which is the oiliness agent based frictionmodifier, the lubricating oil composition according to the third aspectof the present invention has a further improved friction reducingperformance under boundary lubricating conditions, compared to a case inwhich the (C) component is contained alone in the lubricating oilcomposition. Therefore, the lubricating oil composition according to thethird aspect of the present invention can be preferably employed forlubrication of various machines. Especially, since the (B) componentdoes not contain sulfur or phosphorus, it is possible to improve thefriction reducing performance under boundary lubricating conditions withsuppressed increase of sulfur and phosphorus content in the lubricatingoil composition. Therefore, it can be especially preferably used forlubrication of internal combustion engines, specifically for lubricationof internal combustion engines in which sulfur and phosphorus contentand the like that migrates into the exhaust gas are desired to besuppressed (e.g. internal combustion engine equipped with an exhaust gasprocessing apparatus).

EXAMPLES

Hereinafter the present invention will be further specifically describedwith reference to Examples and Comparative Examples. However, thepresent invention is not limited to Examples.

Example 1 and Comparative Examples 1 and 2

As shown in Table 1, the lubricating composition according to the secondaspect of the present invention (Example 1), and lubricating oilcompositions for comparison (Comparative Examples 1 and 2) were eachprepared. To all values of amount of components is applied a unit ofmass % (on the basis of the total amount of composition).

TABLE 1 Exam- Comparative Comparative ple 1 Example 1 Example 2 Base oilGroup II base oil (*1) balance 100 balance Additive 2,4,6- 0.37 — —Triphenylborazine (*2) ZnDTP (*3) — — 1.0 Wear scar diameter (mm) 0.2350.377 0.256 (*1) Hydrocracked mineral oil, sulfur content: 0.00%,saturates content: 97.9%, kinematic viscosity at 40° C.: 91.1 mm²/s,kinematic viscosity at 100° C.: 10.5 mm²/s, viscosity index: 97 (*2) R¹= R³ = R⁵ = H and R² = R⁴ = R⁶ = Ph in the general formula (1) (*3)Primary type

(Evaluation of Friction-Reducing Performance)

For each of the lubricating oil compositions of Example 1 andComparative Examples 1 and 2, friction-reducing performance wasevaluated by means of a ball-on-disk reciprocating friction test machine(SRV friction test machine manufactured by Optimol Instruments, ball:12.7 mm of diameter; disk: 24 mm of diameter and 7 mm of thickness,material of the ball and disk corresponds to SUJ-2), under conditions ofa temperature of 100° C., frequency of 50 Hz, load of 20N, amplitude of1 mm, and examination time of 30 minutes. The value of load 20Ncorresponds to a boundary lubricating condition. The wear scar diameterof ball after the examination is also shown in Table 1.

As can be seen from Table 1, the lubricating oil composition of Example1 which includes the borazine-based additive of the present inventionwas able to reduce the wear scar diameter by approximately 38%, comparedto the lubricating oil of Comparative Example 1 consisting of only thebase oil. In addition, compared to the lubricating oil composition ofComparative Example 2 consisting of the base oil and zincdithiophosphate, the lubricating oil composition of Example 1 was ableto reduce the wear scar diameter by approximately 8%.

From the above results, it was shown that the lubricant additive andlubricating oil composition of the present invention could improvefriction-reducing performance.

Example 2 and Comparative Example 3

As shown in Table 2, the lubricating oil composition according to thesecond aspect of the present invention (Example 2), and a lubricatingoil composition for comparison (Comparative Example 3) were eachprepared. To all values of amount of components is applied a unit ofmass % (on the basis of the total amount of composition).

TABLE 2 Comparative Example 2 Example 3 Base oil Group I base oil A (*1)balance (*3) balance (*3) Group I base oil B (*2) Additive2,4,6-Triphenylborazine (*4) 0.37 — Viscosity index improver 5.3 5.3Additive package (*5) 9.0 9.0 Kinematic viscosity at 40° C. (mm²/s) 70.270.2 Kinematic viscosity at 100° C. (mm²/s) 10.7 10.7 Elemental analysis(mass %) B 0.06 0.03 Ca 0.26 0.26 P 0.07 0.07 Zn 0.08 0.08 N 0.1 0.05 S0.43 0.43 HTT merit (280° C.) 8.5 7.5 HTT merit (290° C.) 7.5 6.5 (*1)Solvent refined mineral oil, sulfur content: 0.12%, saturates content:75%, viscosity index: 100 (*2) Solvent refined mineral oil, sulfurcontent: 0.58%, saturates content: 62%, viscosity index: 97 (*3) Baseoil A/Base oil B = 73/27 (*4) R¹ = R³ = R⁵ = H and R² = R⁴ = R⁶ = Ph inthe general formula (1) (*5) Consisting of ZnDTP, metallic detergent,ashless dispersant, antioxidant, and pour point depressant

(Evaluation of High-Temperature Detergency)

For each of the lubricating oil compositions of Example 2 andComparative Example 3, high-temperature detergency was evaluated bymeans of a hot tube test (conforming to JPI-5S-55 standard).Examinations were carried out at 280° C. and 290° C. Results are alsoshown in Table 2.

As can be seen from Table 2, the lubricating oil composition of Example2 containing the borazine-based additive of the present invention showedgood hot tube merits at both examination temperatures of 280° C. and290° C., compared to the lubricating oil composition of the ComparativeExample 3 which is same as the Example 2 except that the borazine-basedadditive of the present invention is not contained.

From these results, it was shown that the lubricant additive andlubricating oil composition according to the present invention couldimprove high-temperature detergency.

Examples 3 to 6 and Comparative Examples 4 and 5

As shown in Table 3, lubricating oil compositions according to the thirdaspect of the present invention (Examples 3 and 4), lubricating oilcompositions according to the second aspect of the present invention butnot according to the third aspect of the present invention (Examples 5and 6), and lubricating oil compositions for comparison (ComparativeExamples 4 and 5) were each prepared. In Table 3, to all values ofamount of components is applied a unit of mass % (on the basis of thetotal amount of composition).

TABLE 3 Comparative Comparative Example 3 Example 4 Example 5 Example 6Example 4 Example 5 Base oil (A) PAO (*1) balance balance balancebalance balance balance Additive (B) 2,4,6-triphenylborazine (*2) 0.370.37 0.37  0.37 — — (C1) oleylurea (*3) 0.55 — — — 0.55  — (C2)oleylamide (*4) — 1.00 — — — 1.00  (C3) glycerol monooleate — — — 0.63 —— Friction coefficient  0.109  0.114 0.224  0.176 0.146 0.164 (*1) Polyα-olefin base oil, kinematic viscosity at 100° C.: 1.7 mm²/s (*2) In thegeneral formula (1), R¹═R³═R⁵═H and R²═R⁴═R⁶═Ph (*3) In the generalformula (2), p = 1, q = 1, r = 0, R⁷ = —(CH₂)₈CH═CH(CH₂)₇CH₃, andR⁸═R⁹═R¹⁰═H (*4) In the general formula (2), p = 1, q = 0, R⁷ =—(CH₂)₇CH═CH(CH₂)₇CH₃, and R⁹═R¹⁰═H

(Evaluation of Friction Reducing Performance)

For each of the lubricating oil compositions of Examples 3 to 6 andComparative Examples 4 and 5, friction-reducing performance wasevaluated by means of a ball-on-disk type reciprocating friction testmachine (SRV friction test machine manufactured by Optimol Instruments,ball: 12.7 mm of diameter; disk: 24 mm of diameter and 7 mm ofthickness, material of the ball and disk corresponds to SUJ-2). Arunning-in examination was carried out for 30 minutes under frictionconditions of a temperature of 100° C., frequency of 50 Hz, load of 20N,and amplitude of 1 mm; and thereafter, a measurement of frictioncoefficient was carried out under friction conditions of a temperatureof 100° C., frequency of 10 Hz, load of 20N, and amplitude of 1 mm. Thevalue of load 20N corresponds to a boundary lubricating condition.Measurement results of friction coefficient are also shown in Table 3.

As can be seen from Table 3, the lubricating oil compositions ofExamples 3 and 4 were able to reduce the friction coefficient byapproximately 49% or more, compared to the lubricating oil compositionof Example 5 not containing the (C) component. Compared to thelubricating oil compositions of Example 6 containing glycerol monooleatewhich is an oiliness agent based friction modifier which does not fallunder the (C) component, the lubricating oil compositions of Examples 3and 4 were able to reduce the friction coefficient by approximately 35%or more. In addition, compared to the lubricating oil compositions ofComparative Examples 4 and 5 not containing the (B) component, thelubricating oil compositions of Example 3 and 4 were able to reduce thefriction coefficient by approximately 22% or more.

From these results, it was shown that the lubricating oil compositionaccording to the third aspect of the present invention could improvefriction reducing performance under boundary lubricating conditions.

1. A lubricant additive comprising: a borazine compound represented bythe following general formula (1):

(In the formula (1), R¹, R³, and R⁵ are each independently hydrogen, aC1 to C30 hydrocarbyl group, or a C1 to C30 hydrocarbyl group comprisinga heteroatom other than sulfur and phosphorus; and R², R⁴, and R⁶ areeach independently hydrogen, a C1 to C30 hydrocarbyl group, or a C1 toC30 hydrocarbyl group comprising oxygen or boron or nitrogen.).
 2. Thelubricant additive according to claim 1, wherein in the formula (1) R¹,R³, and R⁵ are each independently hydrogen, a C1 to C30 hydrocarbylgroup, or a C1 to C30 hydrocarbyl group comprising oxygen or boron ornitrogen.
 3. The lubricant additive according to claim 1, wherein in theformula (1) R¹, R³, and R⁵ are each independently hydrogen, a C1 to C30hydrocarbyl group, or a C1 to C30 hydrocarbyl group comprising oxygen orboron.
 4. The lubricant additive according to claim 1, wherein in theformula (1), R¹, R³, and R⁵ are the same groups; and R², R⁴, and R⁶ arethe same groups.
 5. A lubricating oil composition comprising: (A) alubricating base oil; and (B) the lubricant additive according toclaim
 1. 6. The lubricating oil composition according to claim 5,further comprising: (C) a friction modifier represented by the followinggeneral formula (2):

(In the formula (2), p is 0 or 1; q is 0 or 1; r is 0 or 1; R⁷ is ahydrocarbyl group having no less than 8 carbon atoms; and R⁸, R⁹, andR¹⁰ are each independently hydrogen or a C1 to C4 hydrocarbyl group.).7. The lubricating oil composition according to claim 6, wherein in theformula (2), at least R⁹ and R¹⁰ are hydrogen; and where p and q are 1,R⁸, R⁹, and R¹⁰ are hydrogen.
 8. The lubricating oil compositionaccording to claim 5, further comprising: one or more selected from thegroup consisting of an ashless dispersant, an antioxidant, a frictionmodifier, a friction-reducing agent, a metallic detergent, a viscosityindex improver, a pour point depressant, a corrosion inhibitor, ananti-rust agent, an anti-emulsifier, a metal deactivator, a defoamer,and a coloring agent.
 9. The lubricating oil composition according toclaim 5, which is a lubricating oil composition for internal combustionengines.
 10. The lubricating oil composition according to claim 6,further comprising: one or more selected from the group consisting of anashless dispersant, an antioxidant, a friction modifier, afriction-reducing agent, a metallic detergent, a viscosity indeximprover, a pour point depressant, a corrosion inhibitor, an anti-rustagent, an anti-emulsifier, a metal deactivator, a defoamer, and acoloring agent.
 11. The lubricating oil composition according to claim6, which is a lubricating oil composition for internal combustionengines.